In a manufacturing process (e.g., a manufacturing process for semiconductor wafers) there are often many steps to be performed in sequence. Typically one or more steps of the process is performed by a particular tool in a sequence of various tools that are utilized in the process. A first sequence of steps of the process is performed by a first tool in the tool sequence. Then a second sequence of steps is performed by a second tool in the tool sequence, and so on until the process is completed. For example, in a semiconductor wafer manufacturing process various tools may perform processes such as diffusion processes, implantation process, etching processes, photomasking processes and interconnection fabrication processes.
A tool operator must periodically perform one or more procedures on a tool to ensure that the tool is operating properly. When a tool experiences a problem and is then subsequently repaired (or even when a tool simply requires routine maintenance), the tool operator performs one or more procedures to “qualify” the tool for return to an operational status. The process of identifying, selecting and performing the “qualification” procedures for a tool is generally referred to as “qualification intervention.”
To more clearly explain the concept of qualification intervention, a semiconductor manufacturing process will be described. It is understood that the principles involved may be generally applicable to many different particular types of manufacturing processes.
FIG. 1 illustrates a block diagram of prior art Manufacturing Execution System (MES) 110 and a prior art Industrial and Financial Systems (IFS) equipment maintenance management system 120 in a semiconductor wafer manufacturing process. MES 110 comprises an automated production process system that controls the manufacture of semiconductor wafers. One well-known system is the WORKSTREAM™ automated system sold by Applied Materials, Inc. of Mountain View, Calif.
Equipment maintenance management system 120 is generally referred to by the initials of its manufacturer Industrial and Financial Systems, Inc. (“IFS”). IFS system 120 comprises an enterprise resource planning application that performs such tasks as monitoring the performance of work orders, coordinating the purchase of parts and materials, scheduling preventative maintenance, and the like.
In the semiconductor wafer manufacturing industry any event that causes semiconductor wafers to be defective is to be avoided. Defective wafers must be thrown away as scrap. To avoid the loss of valuable product as scrap it is very important to minimize the number of incidents that create defective product.
Assume that a piece of manufacturing equipment goes off line and ceases to work. Then a maintenance technician works with the equipment and does something to it (or perhaps does not do anything to it). But the maintenance technician did something with the equipment (even if parts of the equipment were removed and inspected and then subsequently replaced). The equipment then comes back on line and starts making product again. But then the equipment causes the semiconductor wafer products to be defective (“scrap” product). When the cause is investigated it may be determined that the reason that the defective product was created was that (1) the person who worked with the equipment did something that should not have been done, or (2) the person who worked with the equipment did not do something that should have been done, or (3) some other reason caused the defective product to be created.
In the prior art the standard technique for preventing the creation of defective product that is due to someone having worked on a piece of equipment involves performing one or more equipment qualification procedures. When a piece of equipment comes back on line, the equipment operator is supposed to perform one or more procedures to “qualify” the equipment. That is, the equipment operator is supposed to perform one or more procedures to ensure that the equipment is properly operating.
The problem with the prior art method for performing the qualification procedures is that the prior art technique relies upon the operating personnel to properly do the things that they are supposed to do during the qualification procedures. In particular, the operating personnel are required to properly execute the instructions that they are supposed to execute, and to properly interpret the results that they are supposed to interpret. In addition, the prior art method relies upon the operating personnel make judgment calls concerning what should be done during the qualification procedures in the first place. As might be expected, judgment calls that are made by the operating personnel are quite subjective and lead to a wide variation in the type of qualification procedures that are actually performed in any given case.
An additional problem in the prior art method is that the communication between the various operating personnel is accomplished with non-standard types of communication. For example, the operating personnel may communicate through written work instructions, data commonly known to workers in a specific area of operations (referred to as “tribal knowledge”), and informal information interchange.
The operating personnel are human and often make mistakes. Therefore it would be advantageous to have a system and method that minimizes the human error that may occur when qualification procedures are selected and performed on equipment in a manufacturing process.
In order to better understand the nature of a prior art “qualification intervention” process, a prior art qualification intervention process will now be discussed in detail. FIG. 2 illustrates a chart 200 showing a sequence of events that may occur when a scheduled or non-scheduled trigger event occurs in a particular tool (not shown) during the manufacturing process. In the first event shown in FIG. 2 the tool experiences a trigger event (step 210). A scheduled trigger event may be a routine maintenance procedure that is regularly scheduled to be performed. A non-scheduled trigger event may be a malfunction of the tool, an alarm or error message that the tool initiates that indicates that some parameter is out of an allowable range, or an alarm or error message that some other irregular tool performance has been detected.
The tool operator then enters all available information concerning the trigger event into the Manufacturing Execution System (MES) 110. The tool operator enters the description of the trigger event into the MES 110 in the form of text that contains a narrative description what the tool operator observed and what the tool operator thinks the problem, if any, may be. The text message of the narrative description is referred to as a “free text” message. The tool operator sends the “free text” message to the maintenance department, takes the tool offline (i.e., out of production) and logs the tool as “down to maintenance” (step 215).
A maintenance technician receives the “free text” message from the MES 110 and tries to find out the exact nature of the problem, if any, that the tool has experienced. At this point the tool may or may not be exhibiting an original error message that caused the tool operator to create the original “free text” message that described the problem. It may even be that the status of the tool now seems satisfactory and that the “problem” that the tool had is no longer present.
When the tool operator sends a “free text” message to the MES 110 concerning the problem that was detected in the tool, the MES 110 generates a work order (WO) for the problem and sends the work order to the IFS system 120 (step 220). The maintenance technician reviews the work order and determines what steps need to be taken to get the tool running again and ready to go back into production. If the work order indicates that a regularly scheduled maintenance procedure is due, then the maintenance procedure is performed. If the work order indicates the existence of some non-scheduled event that represents a “problem” situation, then the nature of the problem must be determined and corrective steps identified.
The maintenance technician then performs work on the tool (step 225). The work will be either routine maintenance work or, if a problem exists, corrective work such as repair and replacement of parts. The maintenance technician then sends a “free text” message describing the work that has been done to the IFS system 120. The IFS system 120 sends the message to the MES 110. The message explains the nature of the work that the maintenance technician actually performed (step 230). The remarks of the maintenance technician may or may not contain a thorough description of the work that was performed. The “free text” format of the message means that the maintenance technician's narrative description of the remedial work that was performed on the tool may be very subjective. Important features of the work that was performed may be omitted from the remarks. Different maintenance technicians have different levels of writing ability and powers of description. Therefore a substantial variance may exist in the quality of the maintenance reports and their interpretation.
A process engineer then reviews the “free text” message from the maintenance technician. The process engineer then makes a subjective determination concerning which qualification procedures (“Quals”) need to be performed on the tool before the tool can be placed back into production (step 235). This is referred to as the “Qual Define” process. The process engineer then sends a “free text” message to the tool operator that identifies which qualification procedures are to be performed.
Different individual engineers may or may not make the same recommendation for a given case. That is, the selection process for determining which qualification procedures are to be performed may exhibit significant variations. A first process engineer may require only one qualification procedure for a given case, while a second process engineer may require two qualification procedures for the same case. These variations may be due to the differences in knowledge and experience of the two engineers.
The tool operator then performs the qualification procedures on the tool that have been requested by the process engineer (step 240). The tool operator then sends a report to MES 110 verifying that the requested qualification procedures have been performed (step 245). This is referred to as the “Qual Verify” process.
Then the process engineer confirms that the tool operator did perform the requested qualification procedures on the tool (step 250). This is referred to as the “Qual Complete” process. After the “Qual Complete” process has been performed the tool is returned to production (step 255).
The prior art “qualification intervention” process described above is quite cumbersome. Many of the decisions that are required to be made by operating personnel during the process are quite subjective. There are many opportunities in the process for the operating personnel to make errors and create inconsistencies. Notes written by a first individual (e.g., tool operator) must be interpreted by a second individual (e.g., maintenance technician) and notes written by the second individual must be interpreted by a third individual (e.g., process engineer).
Furthermore, there may be long delays between the various steps of the prior art “qualification intervention” process. Consider the streamlined version of the “qualification intervention” process 300 shown in FIG. 3. The streamlined version of the process 300 begins with the action taken by the maintenance technician (step 310). The action may be preventive maintenance (PM) or repair maintenance (RM). This is followed by the “Qual Define” process (step 320), the performance of the qualification procedures (step 330), the “Qual Verify” process (step 340), and the “Qual Complete” process (step 350). Lastly, the tool is returned to production (step 360).
FIG. 4 illustrates a table 400 showing typical delays that are inherent in a “qualification intervention” process 300 of the type shown in FIG. 3. Table 400 was compiled from actual manufacturing runs for a single month in six areas of a semiconductor wafer manufacturing process. The six areas were Diffusion, Implant, Etch, Photo, Interconnect and PECVD (Plasma Enhanced Chemical Vapor Deposition).
For example, consider the Diffusion process. The average delay time for the Diffusion “Qual Define” process was seventy-four (74) minutes. The number of such events was two hundred ninety one (291). This means that the cumulative delay time was fourteen and nine tenths (14.9) days for the Diffusion “Qual Define” process.
The average delay time for the Diffusion “Qual Verify” process was thirty-three (33) minutes. The number of such events was two hundred fifty (250). This means that the cumulative delay time was five and eight tenths (5.8) days for the Diffusion “Qual Verify” process. The average delay time for the Diffusion “Qual Complete” process was twenty-three (23) minutes. The number of such events was three hundred thirty four (334). This means that the cumulative delay time was five and four tenths (5.4) days for the Diffusion “Qual Complete” process. The total number of Lost Tool Days for the Diffusion process was twenty-six and one tenth (26.1) days. Similar figures are shown for the other five areas of the semiconductor wafer manufacturing process.
In view of the above-described deficiencies of the prior art “qualification intervention” process, it would be advantageous to have a system and method for providing an automatic qualification intervention system in a manufacturing process. It would be advantageous to have a system and method that automatically performs the “qualification intervention” process in a manufacturing process.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
The term “controller” means any device, system, or part thereof that controls at least one operation. A controller may be implemented in hardware, software, firmware, or combination thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.
Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as to future uses, of such defined words and phrases.